The present invention relates to a soft magnetic alloy and to its use in a motor for watchmaking.
The hands of analog quartz watches are moved by a miniature electric motor known as Lavet-type stepper motor (see FIG. 1). This motor comprises a bipolar rotor 1 consisting of a permanent magnet, a stator 2 cut from a strip of soft magnetic alloy and a wound core 3 made of soft magnetic alloy possibly different from that of which the stator is made. The stator includes isthmuses 4 and 5 that have to be as narrow as possible.
To manufacture the stator of an electric motor for watchmaking, it is known to use soft magnetic alloys of the 80% nickel alloy type containing a few percent of molybdenum or copper, or of the Fe-36.5Ni-7.5Cr type alloy type or else of the Fe-50Ni-10Cr alloy type. These alloys have a coercive field of less than 100 mOe for thickness between 0.4 and 0.8 mm, within the temperature range from −20° C. to +70° C., and a saturation induction, BS of greater than 4000 gauss at 40° C. However, these alloys are expensive, and it is desirable to have a less expensive alloy. However, such an alloy is not known.